"It is a promise for the future, and their kids are very happy. There's no date set at this time." Pett-Dante also confirmed that Pitt, 48, designed the engagement ring for Jolie, 36, with whom he has six children.

Jewelry maker Robert Procop confirmed he had made the ring in collaboration with Pitt, specifically for the actress, Reuters reported.

"The full creative journey - from conception to completion - took a year, with Brad Pitt waiting until the perfect moment to unveil this special jewel to Angelina Jolie," Procop's spokeswoman said in a statement.

Pitt and Jolie -- dubbed Brangelina by celebrity media -- have been together since 2005, but until now have said they have no plans to marry, Reuters said.

Pitt, who was previously married to "Friends" star Jennifer Aniston, said previously the couple would not wed until gay marriage was legalized in the United States.

But in January he was quoted as saying that the pair were coming under pressure from their three adopted and three biological children, Reuters said.

"It (marriage) seems to mean more and more to our kids. We made this declaration some time ago that we weren't going to do it 'til everyone can. But I don't think we'll be able to hold out," Pitt told The Hollywood Reporter in an interview.

"It means so much to my kids, and they ask a lot. And it means something to me, too, to make that kind of commitment ... But to be in love with someone and be raising a family with someone and want to make that commitment and not be able to it is ludicrous, just ludicrous," he added.

This will be the third time Jolie has got hitched after short-lived marriages to actors Billy Bob Thornton and Jonny Lee Miller.